Bosonic corrections to the effective leptonic weak mixing angle at the two-loop level

Details of the recent calculation of the two-loop bosonic corrections to the effective leptonic weak mixing angle are presented. In particular, the expansion in the difference of the W and Z boson masses is studied and some of the master integrals needed are given in analytic form.Comment: 5 pages, 4 figures, to appear in the proceedings of the 7th International Symposium on Radiative Corrections (RADCOR05), Shonan Village, Japan, 200

Two-loop electroweak fermionic corrections to sin^2 theta_{eff}^{b anti-b}

We present the first calculation of the two-loop electroweak fermionic correction to the flavour-dependent effective weak-mixing angle for bottom quarks, sin^2 theta_{eff}^{b anti-b}. For the evaluation of the missing two-loop vertex diagrams, two methods are employed, one based on a semi-numerical Bernstein-Tkachov algorithm and the second on asymptotic expansions in the large top-quark mass. A third method based on dispersion relations is used for checking the basic loop integrals. We find that for small Higgs-boson mass values, M_H ~ 100 GeV, the correction is sizable, of order O(10^{-4}).Comment: 17 pages, 2 figures, references added, accepted for publication in Nucl. Phys.

Nonmarine stromatolites and the search for early life on Mars

The available evidence permits one to conclude that streams flowed and lakes developed on Mars sometime in the remote past. The lessons learned from the Earth's earliest fossil record suggest that stromatolites might have formed on Mars, speculating that: (1) biopoesis occurred on Mars during its earliest history; (2) life evolved and diversified; (3) life inhabited aqueous environments; and (4) sunlight was an important environmental resource. The most likely place to find stromatolites and possibly microbial fossils on Mars would be in ancient lake and stream deposits. If thermal spring deposits can be identified, then they too are sites for biogeological investigations. Other aspects of this study are presented

Corrections to Quark Asymmetries at LEP

The most precise measurement of the weak mixing angle sin^2(theta) at LEP is from the forward-backward asymmetry e+e- --> bbbar at the Z-pole. In this note the QED and electroweak radiative corrections to obtain the pole asymmetry from the measured asymmetry for b- and c-quarks have been calculated using ZFITTER, which has been amended to allow a consistent treatment of partial two-loop corrections for the b-quark final asymmetries. A total correction of dAfbb=0.0019+/-0.0002 and dAfbc=0.0064+/-0.0001 has been found, where the remaining theoretical uncertainty is much too small to explain the apparent discrepancy between sin^2(theta) obtained from Afbb and from the left-right asymmetry at SLD

Steps towards full two-loop calculations for 2 fermion to 2 fermion processes: running versus pole masses schemes

Recent progress in the calculation of the two-loop on-shell mass counterterms within the electroweak Standard Model (SM) for the massive particles are discussed. We are in progress of developing a package for full two-loop SM calculations of 2 -> 2 fermion processes, with emphasis on the analytical approach where feasible. The complete two-loop on-shell renormalization is implemented. Substantial progress has been made in calculating the master integrals. We are able to compute in an efficient and stable manner up to a few thousands of diagrams of very complex mass structure.Comment: 4 pages, 1 style file. To appear in the proceedings of 9th International Workshop on Advanced Computing and Analysis Techniques in Physics Research (ACAT 03), Tsukuba, Japan, 1-5 Dec 200

ZFITTER: a semi-analytical program for fermion pair production in e+e- annihilation, from version 6.21 to version 6.42

ZFITTER is a Fortran program for the calculation of fermion pair production and radiative corrections at high energy e+e- colliders; it is also suitable for other applications where electroweak radiative corrections appear. ZFITTER is based on a semi-analytical approach to the calculation of radiative corrections in the Standard Model. We present a summary of new features of the ZFITTER program version 6.42 compared to version 6.21. The most important additions are: (i) some higher-order QED corrections to fermion pair production, (ii) electroweak one-loop corrections to atomic parity violation, (iii) electroweak one-loop corrections to nu-e nu-e-bar production, (iv) electroweak two-loop corrections to the W boson mass and the effective weak mixing angle.Comment: 60 pages, latex, 3 table

Longitudinal Top Quark Polarization

Longitudinal polarization of the top quark, averaged over the production angle, is discussed for the top quark produced in e+e- annihilation near its production threshold. It is demonstrated that Coulomb type corrections and rescattering corrections are important. They change considerably measurable quantities and should be taken into account in phenomenological analysis

Complete Two Loop Electroweak Contributions to the Muon Lifetime in the Standard Model

An independent result for the two loop fermionic contributions to the muon lifetime in the Standard Model is obtained. Deviations are found with respect to \cite{Freitas:2000gg}, which result in a shift of the W boson mass by approximately -1.3 MeV over the range of Higgs boson masses from 100 GeV to 1 TeV. Supplied with the bosonic contributions from \cite{Awramik:2002wn,Onishchenko:2002ve,Awramik:2002vu}, this shift, due to the complete electroweak contributions, varies from -2.4 MeV to -0.6 MeV. Additionally, a new test of the matching procedure defining the Fermi constant is presented, which uses fermion masses as infrared regulators.Comment: 11 pages, 5 figures, Tab. 3 corrected, reference adde